In recent decades, with rapid progress of artificial intelligence related technologies, many autonomous humanoid robots have been gradually developed. An ideal autonomous humanoid robot is required to be equipped with sufficient sensing ability of the changes of the surrounding environment (including people, work pieces, and other robots and objects), so as to ensure that the actions of the robot are performed safely and correctly. As such, in addition to sensing and determining the magnitude of compression, a tactile sensor is also required to be able to determine the shear force.
The multi-mode tactile sensors that may simultaneously sense the multi-dimensional stresses have been the subject of research for many years. Nevertheless, owing to limitations of the manufacture equipment, most of the tactile sensors can only be fabricated on a plane and can not be fabricated directly on a curved surface. The process of fabricating the tactile sensors on a curved surface is complicated and costly.